Relay



Oct. 25, 1949. e. c. ARMSTRONG RELAY 2 Sheets-Sheet 1 Filed April 3,1945 ATTORNEY 0 0%? w m 4 n R r a 3 o d, 1 5 M m a @J M% /.V a I c. .v w6 Y F a 6 Q m.

Oct. 25, 1949. G. c. ARMSTRONG RELAY 2 Sheets-Sheet 2 Filed April 5,1945 5 w e z a 0 z a 3 m n z z 4 m a N 2 Wm m mm m :25 3 W/B w 8 z ,7 76 w Q 2 x WITNESSES:

Patented Oct. 25, 1949 RELAY George G. Armstrong, Pittsburgh, Pa.,assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., acorporation of Pennsylvania Application April 3, 1945, Serial No.586,287

9 Claims.

My invention relates to thermally operated electric relays, for instancefor overload protection, and has for its object to provide relays whichcombine especially small size with virtually no contact friction andgood accuracy and constancy of calibration.

In order to achieve these objects, and in accordance with one feature ofmy invention, I provide an electric relay with a heatable containerstructure which contains mercury and a volatile liquid so that themercury is displaced and changes its level when sufficient heat isapplied to volatilize the liquid; and the change in level is used forcausing the mercury to make or break an electric connection betweencontacts associated with the structure. According to other features ofthe invention, I provide a a rigid container for the mercury and equipthe container with a conduit which extends into an upper containerportion where the mercury may be trapped. According to still anotherfeature of the invention, I provide such a relay with means foradlusting the relay for manual or automatic resetting operation.

These and other objects and features of my invention will be apparentfrom the drawings, in which:

Figure 1 is a vertical section through an overload relay according tothe invention;

Fig. 2 is a front view of the same embodiment;

Fig. 3 represents a top view also of the same relay;

Fig. 4 shows a front view of the base portion of the relay;

Figs. 5, 6 and 7 are two different views and a cross section,respectively, of an insulating body which forms part of the frontportion of the relay;

Fig. 8 shows a longitudinal section through the contact andthermo-responsive a ctuating unit of the relay, while Figs. 9 and 10 area top view and a side elevation, respectively, of the same unit;

Fig. 11 is a sectional illustration of a modified form of thethermo-responsive contact unit;

Figs. 12, 13 and 14 show partial and sectional views of three furthermodifications of such a unit.

Referring to the embodiment illustrated in Figs. 1 through 10, and atfirst with particular reference to Figs. 1 through 4, numeral I denotesthe insulating base portion of the apparatus. An insulating body 2 ismounted on the front surface of with four contact terminals denoted by3, 4, 5 and 6, respectively, and best apparent in Fig. 4. Terminals 5and 6 are each provided with a slotted socket l and 8 respectively(Figs. 1 and 4) for the reception of contact pins. Terminals 3 and 4have each a threadedbore to be engaged by 9. connect-- ing screw 9 or lwhich fastens a heater coil II to the removable front portion of theapparatus. Terminals 3 and 4 serve for connecting the t.vo leads of aload circuit to the relay so that the load current flows through theheater coil ll, while terminals and 6 serve to connect to the relay acircuit to be controlled in response to the occurrence of overload inthe load circuit.

The thermo-responsive contact unit to be acted upon by the heater coil His denoted as a whole by numeral l2. It has two contact pins I3 and M(Fig. 1) which in the assembled condition of the relay engage thesockets 1 and 8 thereby conmeeting the contact unit electrically betweenthe terminals 5 and 6. Two ears l5 and it are attached to the contactunit and serve as a bearing for a handle I! which forms an angular leverand is biased by a. spring I8 toward the position the base portion so asto be removable therefrom.

The front face of the base portion I is provided illustrated in Fig. 1.

Details of the thermo-responsive contact unit are illustrated in Figs. 8through According to these figures, the unit 12 has a containerstructure composed of a lower portion l9 and an upper portion bothconsisting of metal. The upper portion 20 is hermetically sealed bymeans of a diaphragm 2| and has a sealing tube 22 for connecting theunit to a vacuum pump during the course of its manufacture. The tube 22is pressed flat and sealed by welding as shown in Fig. 8 when the unitis in finished condition. The lower portion I9 of the container has aninsulating seal 23 through which a contact 24 passes into the interior.Two leads 25 and 26 are attached to the Contact 24 and the wall of theupper container portion 20, respectively, and connect these two partswith the contact pins 14 and I3 (Fig. 1), respectively.

As shown in Fig. 8, a conduit or tube 28 extends from the uppercontainer portion 20 downwardly to near the bottom of the lowercontainer portion IS. The tube 28 in the embodiment of Figs. 8 through10 consists of metal and forms an integral part of the structure 20. Aquantity of mercury, denoted by 21, is disposed in the container portionl9 so that it establishes normally an electric connection between thecontact 24 and the container. Consequently, the circuit between leads 25and 26 or terminals 5 and 6 is normally closed through the mercury. Aquantity of vol- 3 atile liquid denoted b 29 is disposed on top of themercury within the upper space of the container portion Hi. When theportion i9 is heated by the surrounding heater coil (Figs. 1 and 2) toan extent sufficient to volatilize the liquid 29, the increase inpressure thus produced in the upper space of container portion l9 forcesthe mercury column 21 into the tube 28. As a result, the level of themercury in the container space surrounding the tube 28 is lowered untilthe circuit between contact 24 and the container is interrupted. Thisinterruption is used for controlling a protective or indicatingoperation. The volatile liquid may consist of alcohol or of variousother substances which may be selected in accordance with the desiredboiling point.

A stud 35 is soldered to the container portion i9 (Figs. 8 and 10) andserves as an abutment for the return spring |8 of the handle I! (Figs. 1and 2). The container portion 20 is equipped with a mercury trap whichin the embodiment of Figs. 8 through i consists of a valve typemechanism. A valve body 38 forms, at its bottom surface, a conical valvesurface for engagement with a conical seat surface formed at theentrance of the tube 28 into the upper container portion 20. The valvebody 30 is provided with an actuating head 3| with respect to which itis movable in a limited extent in order to permit the valve disk toadjust itself freely on the seat when the valve is moved into closingposition. A Spring 32 tends to hold the valve in the open position asillus trated in Fig. 8. In the assernbledcondition of the relay,however, an adjusting screw 33 seated in the upper arm 34 of the handle(Fig. l) rests against the diaphragm 2| (Fig. 8) and under the bias ofspring i8 (Fig. 1) pushes the actuating head 3| toward the valve seat inopposition to the valve spring 32 permitting the valve body 30 to seatgravitationally. Consequently, the valve is normall closed. When thecontainer structure is heated due to the occurrence of an overloadcurrent in the heater coil and causes the liquid 29 to boil andvolatilize, the pressure exerted on the mercury in the annular spacearound the tube 28 is high enough to force part of the mercury upwardlythrough the tube 28 against the valve body 38 thereby forcing the valveopen and enterin into the upper container portion 20. When the heatingeffect ceases due to a control action caused by the interruption of thecircuit connection between tube 23 and contact 24, the mercury in theupper container portion 20 is trapped by the valve so that thecontrolled circuit remains interrupted. It is then necessary to push thehandle I! against the front face of the relay in order to permit thevalves spring 32 to open the valve so that the trapped mercury flowsback into the bottom portion of the container structure, therebyresetting the relay for a repeat oporation.

It is also possible to design a relay on the principles of m inventionwhich permits the mercury a free return flow upon cessation of the overload in order to reset the relay automatically, or to equip the relaywith selective automatic or manual resetting means. A modification ofthe latter type is exemplified by the embodiment shown in Fig. 11.

The contact unit according to Fig. 11 can be inserted into a relayapparatus otherwise designed in accordance with Figs. 1 through '7. Thecontact unit comprises a container structure composed of a lower portion39 and an upper portion 48. A contact 44 located in the lower portion 28passes through an insulating seal 43 and is provided with a porous body49. which absorbs a quantity of volatile liquid. A quantity of mercurydenoted by 4! establishes an electric connection between the contact 44and a metal tube 48 when the relay is in the illustrated normalcondition. As in the preceding example, the heater coil of the relay,when traversed by a current of sufficient magnitude, causes the absorbedliquid to volatilize and thus increases the pressure in the annularspace above the mercury in the upper part of the container portion 39 sothat the mercury rises in the tube 48. The tube 48 in the embodiment ofFig. 11 is movable in its axial direction and forms a valve surface 50which is biased by a helical compression spring 5| against a conicalseat at the bottom opening of the upper container portion 40. The spring5| abuts against a collar 52 which rests against a substantially rigidclosure plate 53.

The part ofthe tube 48 above the valve surface 50 is provided with twoopenings 54 and 55 and is surrounded by a sleeve 56 which is revolvablebut not axially displaceable relative to the tube 48. A lug 51 attachedto the sleeve 56 and engaging a peripherally extending slot of tube 48,serves to limit the angular displacement of the sleeve 56 and to preventits axial displacement relative to the tube. The sleeve 56 is providedwith two openings 58 and 59. In the illustrated position of the sleeve,the openings 54 and 58 are in registry while the opening 55 is closed bythe sleeve. The upper end of sleeve 56 carries a slotted head 60 whoseneck portion is engaged by the arm 34 of the handle ll.

When the mercury is forced upwardly into the tube 48, due to theabove-mentioned effect of an overload in the heating coil, part of themercury spills through the openings 54 and 58 onto the bottom of theupper container portion where it is trapped. Consequently, uponcessation of the overload conditions, the relay must be reset byactuating the handle l1 thereby pulling the sleeve and tube assemblyupwardly and lifting the valve surface from its seat so that the mercurycan fiow back into the lower container portion.

The relay can be adjusted for automatic resetting by turning the sleevehead 60 so that the opening 59 is placed in registry with the openingwhile the opening 54 is covered by the sleeve 56. Upon the occurrence ofan overload, the mercury is forced through the openings 55 and 59. Sincethese openings are near the bottom of the upper container portion, themercury will flow back during the cooling period of the relay.

The modification represented by Fig. 12 is similar to that of Fig. 11except that it is designed only for manual resetting of the relay. Inthe embodiment of Fig. 12, the tube 48 is provided with a single opening54 and carries the head 60 which, as in the preceding embodiments, isengaged by the arm 34 of the resetting handle. A valve portion 50,forming an integral part with the tube 48, is normally forced by aspring 5| against a seat surface in the bottom of the upper containerportion 40. During overload conditions, the mercury rises in tube 48 andflows through the opening 54 into the bottom section of containerportion 40. When the resetting handle is actuated, the tube 48 with itsvalve disk 50 is lifted in order to permit the return flow of themercury.

The embodiment of Fig. 13 is designed for selective automatic or manualresetting operation, but contains an'interior tube which is immovablyattached to the container structure. The lower container portion 69 ofthe embodiment shown in Fig. 13 is provided with a tube 18 and also witha contact, a quantity of mercury, and a quantity of volatile liquid inorder to operate in accordance with the principle explained in theforegoing. The tube 18 is screwed into the bottom Opening of the uppercontainer portion l1 and hence is not moved during the resettingoperation. The upper part of tube 18 is surrounded by a sleeve 88 whichis revolvable and axially displaceable relative to the tube. The sleeve80 forms a valve disk at 84 which normally closes a connecting duct 85between the upper and lower container portions. The sleeve '80 has aslotted adjusting head 60 in engagement with the arm 38 of the actuatinglever 11. Due to the force of the spring l8, the sleeve 80 is normallypushed downwardly so that the valve disk 84 closes the duct 85. Thesleeve has two openings 86 and 81 to cooperate with two openings 88 and89 of the tube 78. In the illustrated position, the openings 86 and 89are in registry while the opening 88 is covered by the sleeve 80. Duringan overload-responsive operation of the relay, the mercury rising in thetube 18 flows through the openings 89 and 86 onto the bottom of theupper container portion 'HZI. In order to reset the relay, the handlel'l must be pushed against the force of spring l8 so that the valve disk84 is lifted and opens the return duct 85. In order to adjust the relayfor automatic resetting, the head 60 of sleeve 80 is turned by means ofa screw driver so that the opening 89 is covered by the sleeve while theopening 81 is placed in registry with the opening 88. The rising mercurycan then enter through the openings 88 and 81 into the upper portion 10and is free to flow back through the same openings when the heater coolsdown to normal temperature.

The relay partially represented in Fig. 14 has its mercury containerprovided with a closure plate 94 of porous material whose pores aresmall enough to prevent the loss of mercury but suiliciently large topermit the slow passage of gases in order to avoid the development ofback pressure within the upper container portion 90 and to maintain theinternal pressure equal to the external atmospheric pressure, thusfixing the boiling'point of the volatile liquid. The upper containerportion 90 is further provided with means for protecting the mercuryfrom oxidizing under the influence of air which may enter through thepores of the plate 94. In other respects the embodiment of Fig. 14 maybe similar to the modifications previously described. More in detail,the interior tube 9| according to Fig. 14 is screwed at 92 into thebottom of the upper container portion 90; and a ring 83 of felt or thelike absorbent material is placed close to the bottom of the uppercontainer portion to be contacted by the mercury when it rises into 'theupper portion through the opening 85. The

body 83 is saturated with a protective liquid such as dibutyl phthalatewhich wets the surface of the mercury and does not evaporate under alloperating conditions of the relay while exerting no chemical efiect onthe mercury and the other materials of the construction. The mercurytrapped in the upper container portion is permitted to flow through thehole 96 back into the tube 9| when this hole is opened by lifting themember 91.

Relays according to the invention and as described in the foregoing canbe manufactured with extremely small over-all dimensions as comparedwith known contact relays of comparable current capacity. The electriccreepage distances of relays according to the invention are alsovfavorably large. These advantages in conjunction with the small compassof the device are particularly important for using the relays as acomponent part of line starters and machine tool controls where space isat a premium. Since the boiling point of the volatile liquid in relaysaccording to the invention is fixed and since the use of mercury avoidsthe effects of friction and of variable spring pressure, the relayavoids not only most of the causes of failure occurring with relays ofother types, but has also the high constancy of performance andrecalibration.

The various modifications described in the foregoing will indicate tothose skilled in the art that the invention is not limited to thespecific embodiments shown in the figures, but can be modified asregards various details without departure from the essential features ofthe invention as set forth in the claims annexed hereto.

I claim as my invention:

1. An electric relay comprising a container structure having a lowerportion and an upper portion separated from each other, a conduitforming a communication between said container portions, a quantity ofmercury normally enclosed by said lower portion, a quantity of volatileliquid disposed within said lower portion above said mercury, heatingmeans for causing said liquid to volatilize in order to push mercurythrough said conduit into said upper portion, valve means effectivebetween said conduit and said upper portion and being displaceablebetween two positions to permit the flow of mercury only in thedirection from said lower portion into said upper portion when in one ofsaid positions while permitting the flow oi mercury in said direction aswell as in the opposite direction when in said other position, adjustingmeans for selectively placing said valve means into said respectivepositions, and manually operable resetting means for releasing saidvalve means when set in said one position so that then the return flowof mercury from said upper portion to said lower portion occurs onlyupon actuation of said resetting means, and insulated contactsassociated with said container structure to be electricallyinterconnected and disconnected by said mercury depending upon thechange in mercury level caused by said heating means.

2. An electric relay comprising a container structure having a lowerportion and an upper portion, a conduit opening into said upper portionand extending downwardly into the lower portion, said conduit havingwithin said lower portion a smaller cross section than said lowerportion so that an annular space exists around said conduit at the topof said lower portion a quantity of mercury normally disposed in saidlower portion so as to have its level above the 7 by said heating means,valve means disposed within said upper portion for preventing, wheneffective, a return flow of mercury into said lower portion uponoperation of said heating means, and control means exteriorly operablefor selectively rendering said valve efiective and ineffective.

3. An electric relay comprising a container structure having a lowerportion and an upper portion, a conduit opening into said upper portionand extending downwardly into the lower portion, a quantity of mercurynormally disposed in said lower portion so as to have its level abovethe lower opening of said conduit, a quantity of volatile liquiddisposed in the space surrounding said conduit in said lower portionabove said mercury, heating means for causing said liquid to volatilizein order to push mercury through said conduit into said upper portion,insulated contacts associated with said container structure to beelectrically interconnected and disconnected by said mercury dependingupon the change in mercury level caused by said heating means, saidconduit being longitudinally displaceable and forming a valve member,said upper portion forming a seat for said valve member so that themercury is prevented from flowing from said upper portion back into saidlower portion, and exteriorly operable control means for displacing saidconduit in order to lift said valve member from said seat in order topermit such return flow.

4. An electric relay comprising a container structure having a lowerportion and an upper portion separated from each other, a conduitforming acommunication between said container portions and extendingfrom near the bottom of said lower portion to above the bottom of saidupper portion, a quantity of mercury normally enclosed by said lowerportion, a quantity of volatile liquid disposed in the space surroundingsaid conduit within said lower portion above said mercury, heating meansfor causing said liquid to volatilize in order to push mercury throughsaid conduit into said upper portion so that it spills onto the bottomof said upper portion, a communication between the bottom of said upperportion and said lower portion, exteriorly operable control means foropening and closing said communication, and insulated contactsassociated with said container structure to be electrically connectedand disconnected by said mercury depending upon the change in mercurylevel caused by said heating means.

5. An electric relay comprising a container structure having a lowerportion and an upper portion separated from each other, a conduitforming a communication between said container portions and extendingfrom near the bottom of said lower portion to above the bottom of saidupper portion, a quantity of mercury normally enclosed by said lowerportion, a quantity of volatile liquid disposed in the space surroundingsaid conduit within said lower portion above said mercury, heating meansfor causing said liquid to volatilize in order to push mercury throughsaid conduit into said upper portion so that it spills onto the bottomof said upper portion, said conduit being normally open toward saidupper portion at a place-above the bottom of said upper portion andhaving a controllable opening toward said upper portion at a placecloser to said bottom, exteriorly operable control means for opening andclosing said opening, and insulated contacts associated with saidcontainer structure to be electrically connected and disconnected bysaid mercury depending upon the change in mercury level caused by saidheating means.

6. An electric relay comprising a container structure having a lowerportion and an upper portion separated from each other, a, conduitforming a communication between said container portions and extendingfrom near the bottom of said lower portion to above the bottom of saidupper portion, a quantity of mercury normally enclosed by said lowerportion, a quantity of volatile liquid disposed within said lowerportion above said mercury, heating means for causing said liquid tovolatilize in order to push mercury through said conduit into said upperportion so that it spills onto the bottom 0! said upper portion, saidconduit being normally open toward said upper portion at a place abovethe bottom of said upper portion and having a controllable openingtoward said upper portion at a place closer to said bottom, a perforatedsleeve revolvably seated on said conduit for covering and closing saidopening, exteriorly operable means for revolving said sleeve, andinsulated contacts associated with said container structure to beelectrically connected and disconnected by said mercury depending uponthe change in mercury level caused by said heating means.

7. An electric relay comprising a container structure having a lowerportion and an upper portion separated from each other, a conduitforming a communication between said container portions and extendingfrom .near the bottom of said lower portion to above the bottom of saidupper portion, a quantity of mercury normally enclosed by said lowerportion, a quantity of volatile liquid disposed within said lowerportion above said mercury, heating means for causing said liquid tovolatilize in order to push mercury through said conduit into said upperportion so that it spills onto the bottom of said upper portion, saidconduit being normally open toward said upper portion at a place abovethe bottom of said upper portion and having a controllable openingtoward said upper portion at a place closer to said bottom, a perforatedsleeve revolvably seated on said conduit for covering and closing saidopening, exteriorly operable means for revolving said sleeve, in orderto thereby set the relay for automatic or manual resetting, and normallyclosed valve means forming when opened a communication between saidupper and lower portions and being exteriorly operable to permit thereturn flow of mercury by manual resetting of the relay.

8. An electric relay comprising a container having a bottom portionprovided with a quantity of mercury and containing an absorptive bodyabove said mercury provided with volatile liquid, a conduit extendingupwardly from said bottom portion, heating means for catsing said liquidto volatilize in order to push mercury through said conduit into saidupper portion, and insulated contacts associated with said containertobe electrically interconnected and disconnected by said mercurydepending upon the change in mercury level caused by said heating means.

9. An electric relay comprising, a container structure having a lowerportion and an upper portion separated from each other, a conduitforming a communication between said container portions, a quantity ofmercury normally enclosed by said lower portion, a quantity of volatileliquid disposed within said lower portion above said mercury, heatingmeans for causing said liquid to volatilize in order to push mercury 910 through said conduit into said upper portion, and insulated contactsassociated with said container REFERENCES CITED structure to beelectrically interconnected and The following references are of recordin the disconnected by said mercury depending upon file of this patent:the change in mercury level caused by said heat- 5 ing means, and anabsorptive body arranged in UNITED STATES PA'I'EN'I'S said upper portionto be contracted by the mer- Number Name Date cury and provided withprotective liquid for pre- 760,281 Trull May 17, 1904 venting oxidationof the mercury. 1,556,134 Stoekie 1 Oct. 6, 1925 10' 1,571,182 Barnum eta1. Feb. 2, 1926 GEORGE C. ARMSTRONG. 1.695.546 Goodhue Dec. 18 1928

